JP3050684B2 - Trace ion analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to an apparatus for quantitatively analyzing trace ions such as silicate ions contained in pure water used in the production of semiconductors.

[0002]

2. Description of the Related Art Pure water used in the production of semiconductors, for example, is required to have a low concentration of total silicon dioxide from the viewpoint of improving the production yield and the reliability of products. However, since there is no method or means for directly quantifying total silicon dioxide in water, conventionally, silicate ions have been quantified and, based on this, total silicon dioxide has been determined. As a conventional method, there is a method in which a sample liquid injected into an electrolyte eluate is separated by a separation column, and then a mixture with a reaction reagent is quantified by a detector.

FIG. 3 shows a trace ion analyzer for carrying out the above-mentioned quantification method. In this figure, reference numeral 1 denotes a sample injection unit, for example, a 6-way switching valve having six ports 1a to 1f. Consisting of A sample liquid supply line 2, an electrolyte eluent supply line 3, and a separation column 4 are connected to the sample injection section 1.

That is, the sample liquid supply line 2 is connected to a port 1a, and the upstream side thereof is connected to a sample liquid supply source (not shown) via a pump (not shown). The electrolyte eluent supply line 3 is connected to the port 1d, includes a pump 5 and a deaerator 6, and is connected on the upstream side to an electrolyte eluent tank 8 provided with a carbon dioxide gas trap 7. ing. Further, the separation column 4 is connected to the port 1c via the flow path 9 and has, for example, an anion exchange resin therein. Note that 10 is the port
A sample loop 11 connects between 1b and 1e. A sample liquid discharge line 11 is connected to the port 1f and includes a waste liquid tank 12.

[0005] Reference numeral 13 denotes a mixing joint provided on the outlet side of the separation column 4, and a reaction reagent supply line 14 and a reactor 15 are connected to the mixing joint 13. The reaction reagent supply line 14 includes a pump 16 and a deaerator 17, and the upstream side thereof is connected to a reaction reagent tank 18. Further, the reactor 15 is connected to a detector 20 such as an absorptiometer via a cooling coil 19. Reference numeral 21 denotes a pump connected to the deaerators 6 and 17, 22 denotes a waste liquid tank connected to the detector 20 via a back pressure coil 23, 24 denotes a recorder, and 25 denotes a data processing device. Further, the separation column 4 and the cooling coil 19, the mixing joint 13 and the reactor 15
Are stored in appropriate thermostats, respectively.

[0006] In the trace ion analyzer configured as described above, by supplying the sample solution and the electrolyte eluent to the separation column 4, silicate ions, which are target components to be quantified, are separated from other components. Thereafter, in the mixing joint 13, the liquid containing the separated silicate ions and the coloring reaction reagent are mixed, and the mixed liquid is allowed to react in the reactor 15, so that the selectivity is high,
And highly sensitive measurement can be performed.

[0007]

However, when a large amount (for example, 200 μl) of ultrapure water as a sample solution is injected into the above-mentioned trace ion analyzer and silicate ions are quantified, FIG. As shown in the chromatogram, the blank value is large, the tailing of the peak takes a long time, and the peak becomes abnormally high in the low concentration region of the target component as shown by the calibration curve indicated by the imaginary line A in FIG. Since a phenomenon occurs, there is a problem that improvement in sensitivity cannot be expected.

Here, the cause of the occurrence of the abnormal peak will be considered. When a large amount of the sample solution is injected into the electrolyte eluent, a zone of the sample solution is formed in a part of the electrolyte eluate. When the sample liquid zone reaches the separation column 4, each ion in the sample liquid is separated into the electrolyte eluent in a time series based on the interaction with the ion exchange resin of the separation column 4.

However, a large amount of pure water sample containing only a very small amount of ions (for example, 200 μl)
Above) When injected, a zone of pure water containing almost no ions is formed in a part of the electrolyte eluent. When the pure water zone reaches the separation column 4, the electric conductivity of the pure water zone is extremely low, and the silicate ion concentration is also low. It is presumed that a part of the effluent flows out and a peak much higher than the silicate ion concentration contained in the pure water sample occurs.

On the other hand, as shown in, for example, JP-A-3-15754, a concentration column is provided on the upstream side of the separation column, and the concentration treatment is carried out prior to the separation treatment of the sample liquid to substantially reduce the amount of the sample liquid. It has been proposed to increase the sensitivity by injecting a sample of, for example, 200 μl or less). However, according to this conventional technique, there is a drawback that the configuration becomes complicated and expensive due to the provision of the concentration column. Even in this case, it has been difficult to sufficiently increase the sensitivity.

The present invention has been made in consideration of the above-mentioned matters, and the object thereof is to provide a simple device.
An object of the present invention is to provide a trace ion analyzer capable of performing accurate and highly sensitive measurement even when a large amount of pure water sample is injected as a sample liquid.

[0012]

In order to achieve the above object, the present invention relates to a method for injecting a sample solution into an electrolyte eluent at the outlet side of a sample injecting section for injecting the sample solution into the electrolyte eluent. The liquid is continuously mixed with the electrolyte eluent bypassing the sample injection section.

[0013]

According to the above construction, even when a large amount of pure water sample containing only a trace amount of ions is injected as a sample liquid, the pure water sample is continuously connected to the electrolyte eluent at the outlet of the sample injection section. , No zone with extremely low electrical conductivity is formed in the separation column. Therefore, ions that have been equilibrium-adsorbed to the ion exchange resin in the separation column do not elute into the pure water sample. As a result, the occurrence of abnormal peaks in the low concentration range of the target component is suppressed, and the blank value is reduced, so that accurate and highly sensitive measurement can be performed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same components as those shown in FIG. 3 are the same.

FIG. 1 shows an example of a trace ion analyzer according to the present invention. This trace ion analyzer is largely different from the conventional one shown in FIG. That is, the electrolyte eluent supply line 3 and the flow path 9 on the downstream side of the sample injection section 1 are connected by a bypass line 26.

Next, a description will be given of a case where silicate ions in, for example, ultrapure water are quantified in the trace ion analyzer configured as described above. In this case, a KOH eluent is used as an electrolyte eluent, and a sulfuric acid coloring solution containing ammonium molybdate is used as a reaction reagent. After the electrolyte eluent and the reaction reagent are degassed by the deaerators 6 and 17, respectively, the pumps 5 and 16 are respectively supplied to the electrolyte eluent supply line 3 and the reaction reagent supply line 14 at constant flow rates.

On the other hand, by switching the switching valve as the sample injection section 1, pure water supplied by the sample liquid supply line 2 is injected into the electrolyte eluent supplied by the electrolyte eluent supply line 3. You. At this time, the electrolyte eluent flowing through the electrolyte eluent supply line 3 flows continuously through the bypass line 26 on the outlet side of the sample injection unit 1.

Therefore, on the outlet side of the sample injection part 1, the pure water injected into the electrolyte eluent and the electrolyte eluate bypassing the sample injection part 1 are continuously mixed. The mixed liquid is introduced into the separation column 4 to separate silicate ions from other ions. Then, the liquid containing silicate ions reaches the mixing joint 13 where it is mixed with the reaction reagent, and both react in the reactor 15. Next, this reaction solution is cooled by a cooling coil 19, and then introduced into an absorption photometer 20 as a detector, where the absorbance is measured, and the silicate ion concentration is obtained from the peak value.

FIG. 4 (B) shows a chromatogram obtained by quantification using the trace ion analyzer having the above-mentioned structure. When this chromatogram is compared with the conventional one shown in FIG. It can be seen that the blank value has been significantly reduced and the tailing of the peak has been significantly shortened. The solid line B in FIG. 5 shows the calibration curve at this time. Compared with the conventional curve shown by the virtual line A in FIG. 5, the peak is abnormal in the low concentration region of the target component. It can be seen that it is no longer high.

This is considered to be due to the fact that a pure water sample zone having an extremely low electric conductivity was not formed, so that the occurrence of an abnormal peak in a low concentration region of the target component was suppressed. Therefore, according to the present invention, measurement can be performed with high sensitivity even when a large amount of sample liquid is injected. It was found that the sensitivity could be measured.
In addition, the lower limit of detection of silicate ions has been extended to 0.1 ppb.

FIG. 2 shows another embodiment of the present invention. In this embodiment, the electrolyte eluent supply line 3 is branched on the upstream side of the deaerator 6 instead of the bypass line 26. A second electrolyte eluent supply line 27 is provided in parallel with the electrolyte eluent supply line 3, and a deaerator 28, a pump 29, and a mixing joint 30 are sequentially provided from the upstream side thereof, and a sample injection unit 1 is provided. Port 1d is connected to the inlet side of the mixing joint 30. It goes without saying that even in the case of such a configuration, the same effect as that of the above embodiment can be obtained.

It goes without saying that the present invention can be widely applied to other than quantitative analysis of silicate ions contained in pure water.

[0023]

As described above, according to the present invention,
Even when a large amount of the sample solution was injected, the measurement could be performed with high sensitivity, and it was easy to detect extremely minute trace ions.
There is also an advantage that there is no need to provide a concentration column and the configuration is simple.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration example of a trace ion analyzer according to the present invention.

FIG. 2 is a diagram schematically showing another configuration example of the trace ion analyzer according to the present invention.

FIG. 3 is a diagram schematically showing a configuration of a conventional trace ion analyzer.

FIG. 4A is a diagram showing a chromatogram obtained when silicate ions in pure water are quantified by a conventional apparatus, and FIG. 4B is a figure showing quantification of silicate ions in pure water by the apparatus of the present invention. FIG. 5 is a diagram showing a chromatogram obtained when the above-mentioned process is performed.

FIG. 5 is a diagram showing a calibration curve obtained when silicate ions in pure water are quantified.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... sample injection part, 3 ... electrolyte eluent supply line, 4 ... separation column, 13 ... mixing joint, 14 ... reaction reagent supply line, 15 ... reactor, 20 ... detector.

Claims (1)

(57) [Claims] An electrolyte eluent supply line and a separation column are connected to a sample injection section to inject a sample solution into the electrolyte eluate, and provided at an outlet side of the separation column. A reaction reagent supply line and a reactor are connected to the mixing joint, and further, in a trace ion analyzer in which a detector is connected to the downstream side of the reactor, the electrolyte eluate is provided at the outlet side of the sample injection section. A trace ion analyzer characterized in that the injected sample liquid and the electrolyte eluent bypassing the sample injection section are continuously mixed.